This is for testing Linux, as it is better then any other operating system.
This is for testing Windows, as it is better then any other operating system.
This is for testing Solaris, as it is better then any other operating system.
This is for testing Mac, as it is better then any other operating system.
This is for testing Linux, as it is better then any other operating system.
.... And so on!

I want to filter and display only those lines which contains all 3 strings (i.e. words) "Solaris", "better" "system". How can I achieve this?

One more thing, egrep '(string1|string2) or grep -E '(string1|string2)' displays all lines that either contains both strings or string1 or string2, but I want only those lines having both strings. Although it can be achieved simply by using grep cmd multiple times for every string, but don't want this. So is there any replacement for this?

sag47

11-01-2012 10:50 AM

By default bash uses Basic Regular Expressions (BRE). This means certain regular expression characters lose their special meaning so you'll have to use the backslash escape character to give it special meaning again...

Code:

grep 'Solaris\|better\|system' somefile

To match all words you'll require multiple grep statements because non-matching lines will be filtered out with each subsequent grep.

Code:

grep 'Solaris' somefile | grep 'better' | grep 'system'

More on regex and grep
From the grep (GNU grep) 2.10 man page...

Quote:

grep understands three different versions of regular expression syntax: “basic” (BRE), “extended” (ERE) and “perl" (PRCE). In GNU grep, there is no difference in available functionality between basic and extended syntaxes. In other implementations, basic regular expressions are less powerful.

-F, --fixed-strings
Interpret PATTERN as a list of fixed strings, separated by newlines, any of which is to be matched. (-F is
specified by POSIX.)

-G, --basic-regexp
Interpret PATTERN as a basic regular expression (BRE, see below). This is the default.

-P, --perl-regexp
Interpret PATTERN as a Perl regular expression (PCRE, see below). This is highly experimental and grep -P
may warn of unimplemented features.

Read your local grep man page for what options are specifically available for you. All greps are not equal.

shivaa

11-01-2012 11:09 AM

Thanks @sag47. But the actual situation is little different. File contains lakhs of entries in it with different patterns. So using grep 3 or 4 or multiplpe times is the only option to get desired output? Or is their any better alternative?

sag47

11-01-2012 12:04 PM

Quote:

Originally Posted by shivaa
(Post 4819751)

Thanks @sag47. But the actual situation is little different. File contains lakhs of entries in it with different patterns. So using grep 3 or 4 or multiplpe times is the only option to get desired output? Or is their any better alternative?

grep operates on the stream unlike programs like sort (which takes in all the input and then presents output). So using grep in this manner does not change performance whether you're using it once or 10 times.